JButton listener not firing

Question

I seperated my codes into MVC model and now my confirm button action listener is not printing the username and password even though I added a Actionlistener for it. please help thanks.

Codes

LoginDialog.java

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;

@SuppressWarnings("serial")
public class LoginDialog extends JDialog {

    private JLabel nameLabel;
    private JLabel passwordLabel;
    private JTextField usernameTF;
    private JPasswordField passwordTF;
    private JButton confirmBtn;
    private JButton cancelBtn;
    private JPanel topPanel;
    private JPanel buttonPanel;
    private GridBagConstraints gbc;

    public LoginDialog() {
        this.setTitle("Authentication");

        topPanel = new JPanel(new GridBagLayout());
        buttonPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));
        nameLabel = new JLabel("Name : ");
        passwordLabel = new JLabel("Password : ");
        usernameTF = new JTextField();
        passwordTF = new JPasswordField();
        confirmBtn = new JButton("Confirm");
        cancelBtn = new JButton("Cancel");
        buttonPanel.add(confirmBtn);
        buttonPanel.add(cancelBtn);
        gbc = new GridBagConstraints();

        gbc.insets = new Insets(4, 4, 4, 4);

        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.weightx = 0;
        topPanel.add(nameLabel, gbc);

        gbc.gridx = 1;
        gbc.gridy = 0;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.weightx = 1;
        topPanel.add(usernameTF, gbc);

        gbc.gridx = 0;
        gbc.gridy = 1;
        gbc.fill = GridBagConstraints.NONE;
        gbc.weightx = 0;
        topPanel.add(passwordLabel, gbc);

        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 1;
        gbc.gridy = 1;
        gbc.weightx = 1;
        topPanel.add(passwordTF, gbc);

        this.add(topPanel);
        this.add(buttonPanel, BorderLayout.SOUTH);
    }

    public void showLoginDialog() {
        LoginDialog ld = new LoginDialog();
        ld.setSize(400, 150);
        ld.setVisible(true);
        ld.setLocationRelativeTo(null);
    }

    public String getUsername() {
        return usernameTF.getText();
    }

    public String getPassword() {
        return new String(passwordTF.getPassword());
    }

    public void confirmBtnListner(ActionListener listener) {
        confirmBtn.addActionListener(listener);
    }
}

Controller.java

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class Controller {

    private LoginDialog loginDialog;

    public Controller(LoginDialog loginDialog) {
        this.loginDialog = loginDialog;
        loginDialog.showLoginDialog();
        loginDialog.confirmBtnListner(new BtnListener());
    }

    class BtnListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            System.out.println(loginDialog.getUsername());
            System.out.println(loginDialog.getPassword());
        }
    }

    public static void main(String[] args) {
        LoginDialog loginDialog = new LoginDialog();
        new Controller(loginDialog);
    }
}

Answer 1

You are having two instances of LoginDialog class.

One you are creating in your controller and the other one is in your LoginDialog#showLoginDialog() method.

Let's list them:

1st instance - In the controller class named `loginDialog`
2nd instance - In the `LoginDialog` class named `ld`  

Here ld is an object created within loginDialog object. But they are two different JDialog objects. When you call

loginDialog.showLoginDialog()  

another object ld is created from within the method. The JDialog refered is set to visible by:

ld.setVisible(true)

So now,

Object `ld` is visible
And Object `loginDialog` is NOT yet visible as you havent done `loginDialog.setVisible(true)` yet.

Now are adding the ActionListener to the button within loginDialog object, which is not yet visible. While there is no ActionListener added to the Button within ld object.

Final conclusion:

1. Object ld is visible, but button within it has NO ActionListener.
2. Object loginDialog is NOT yet visible. But the button within it has an ActionListener.
3. The button you are clicking is a part of ld object which has NO action listener associated to it.
4. The button which has an ActionListener associated to it is a part of loginDialog object which is NOT visible.

Wanna check if I am right?

Just add these lines in your controller constructor:

loginDialog.setVisible(true);
loginDialog.setSize(400, 150);
loginDialog.setLocationRelativeTo(null);  

I won't give you the full solution as we don't spoonfeed here on stack overflow. So it's a challange for you to adjust your code accordingly. :)

Answer 2

The method showLoginDialog() creates a new instance of your dialog, which does not have the actionlistener.

fix: don't create a new instance - use the one you have.

    public void showLoginDialog() {
        setSize(400, 150);
        setVisible(true);
        setLocationRelativeTo(null);
    }